linux-kernel - [PATCH] ipmi:ssif: Improve detecting during probing

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Message-ID: <ZsU9SRlQgzQn8bDs@mail.minyard.net>
Date: Tue, 20 Aug 2024 20:05:13 -0500
From: Corey Minyard <corey@...yard.net>
To: "Ivan T. Ivanov" <iivanov@...e.de>
Cc: openipmi-developer@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: [PATCH] ipmi:ssif: Improve detecting during probing

If an IPMI SSIF device is probed and there is something there, but
probably not an actual BMC, the code would just issue a lot of errors
before it failed.  We kind of need these errors to help with certain
issues, and some of the failure reports are non-fatal.

However, a get device id command should alway work.  If that fails,
nothing else is going to work and it's a pretty good indication that
there's no valid BMC there.  So issue and check that command and bail
if it fails.

Reported-by: Ivan T. Ivanov <iivanov@...e.de>
Signed-off-by: Corey Minyard <corey@...yard.net>
---
 drivers/char/ipmi/ipmi_ssif.c | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

Ivan, is it possible for you to test this patch on the broken system?
It should work based on what you reported, but it's nice to be sure.

Also, I discovered that the detect function is kind of bogus, it only
works on an address list that isn't present (any more).  However, I
re-used it for my purposes in the probe function.

Thanks.

diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
index e8e7b832c060..4c403e7a9fc8 100644
--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -1368,8 +1368,20 @@ static int ssif_detect(struct i2c_client *client, struct i2c_board_info *info)
 	rv = do_cmd(client, 2, msg, &len, resp);
 	if (rv)
 		rv = -ENODEV;
-	else
+	else {
+	    if (len < 3) {
+		rv = -ENODEV;
+	    } else {
+		struct ipmi_device_id id;
+
+		rv = ipmi_demangle_device_id(resp[0] >> 2, resp[1],
+					     resp + 2, len - 2, &id);
+		if (rv)
+		    rv = -ENODEV; /* Error means a BMC probably isn't there. */
+	    }
+	    if (!rv && info)
 		strscpy(info->type, DEVICE_NAME, I2C_NAME_SIZE);
+	}
 	kfree(resp);
 	return rv;
 }
@@ -1704,6 +1716,16 @@ static int ssif_probe(struct i2c_client *client)
 		ipmi_addr_src_to_str(ssif_info->addr_source),
 		client->addr, client->adapter->name, slave_addr);

+	/*
+	 * Send a get device id command and validate its response to
+	 * make sure a valid BMC is there.
+	 */
+	rv = ssif_detect(client, NULL);
+	if (rv) {
+		dev_err(&client->dev, "Not present\n");
+		goto out;
+	}
+
 	/* Now check for system interface capabilities */
 	msg[0] = IPMI_NETFN_APP_REQUEST << 2;
 	msg[1] = IPMI_GET_SYSTEM_INTERFACE_CAPABILITIES_CMD;
-- 
2.34.1